KR20180097610A - Polymer emulsion as binder for conductive compositions - Google Patents

Abstract

The present invention provides a metal conductive composition having improved conductivity. Improved conductivity is due to sintering and addition of polymer emulsions.

Description

Polymer emulsion as binder for conductive compositions

Provided herein are conductive compositions having improved conductivity. The improved conductivity is due to the addition of at least one polymer emulsion and at least one sintering agent as a binder to the conductive composition having metal particles.

Conductive compositions are known. Examples are conductive inks used in printed electronic applications. One of the major components used to impart conductivity to their compositions is silver. In recent years, silver prices have fluctuated significantly, making it difficult for manufacturers to manage their product lines. Research and development studies related to conductivity have become popular in recent years.

To date, various approaches have been used to produce conductive compositions and to improve the conductivity of such compositions. For example, a silver complex is introduced into the composition, and then the composition is exposed to elevated temperature conditions such as above 150 DEG C to decompose the silver complex. After the decomposition of the silver complex, silver nanoparticles capable of improving the electrical conductivity are formed in the reaction system. However, many applications that are sensitive to heat require processing temperatures below 150 ° C.

With the development of flexible electronic devices, the use of thermally sensitive substrates is becoming more and more common in the electronics industry, creating a strong demand for materials with high electrical conductivity after processing at temperatures below 150 ° C. For example, there is an urgent need to reduce the bezel width and improve the electrical conductivity of the bezel line in touch screen sensors due to advances in mobile technology and consumer aspirations of larger screens and narrower bezels.

Accordingly, it would be desirable to provide an alternative solution to the difficulties imposed by the manner in which electrical conductivity is achieved using known conductive ink compositions.

The present invention provides such a solution.

Broadly speaking, the present invention provides a sinterable conductive composition comprising:

A metal component having an average particle diameter of greater than about 5 nm to about 100 mu m;

Subpayment; And

An emulsion comprising water and at least one polymer having an average particle diameter of about 5 nm to 1000 mu m.

In a more particular embodiment, the present invention provides a sinterable conductive composition comprising:

Metal components made or doped with silver, aluminum, gold, germanium or oxides or alloys thereof having an average particle diameter of greater than about 5 nm to about 100 mu m;

Phosphoric acid, phosphonic acid, formic acid, acetic acid, hydrogen halides and halide salts of metals of Groups I and II; And

An emulsion comprising water and at least one polymer having an average particle diameter of about 5 nm to 1000 mu m.

In another more particular aspect, the present invention provides a sinterable conductive ink composition comprising:

A metal component having an average particle diameter of greater than about 5 nm to about 100 mu m; And

An emulsion comprising at least one polymer grafted with water and an organohalogen moiety having an average particle diameter of from about 5 nm to about 100 mu m.

In another aspect, the invention provides a method of improving the electrical conductivity of a conductive composition, comprising the steps of:

Providing an emulsion comprising water and at least one polymer having an average particle diameter of from about 5 nm to about 100 [mu] m;

Providing a sub-settling to the emulsion;

Providing a metal component to the emulsion having an average particle diameter of greater than about 5 nm to about 100 mu m to form a conductive composition; And

Exposing the conductive composition to a temperature of from room temperature to about 200 < 0 > C for a time sufficient to sinter the conductive composition.

In yet another aspect, the invention provides a substrate on which a composition of the present invention is disposed.

In yet another aspect, the present invention provides an emulsion comprising at least one polymer grafted with water and an organohalogen moiety.

In any of these embodiments or aspects, the polymer may have a molecular weight of Tg and / or from about 200,000 M _w of more than 70 ℃.

This emulsion provides improved conductivity to the composition by assisting the metal particles to form a sintered network.

In addition, since the emulsion contains water as a component, it promotes health, safety and environmental benefits as compared to solvent base emulsions that play a similar role.

Figure 1 depicts SEM images of Control 1 and Sample No. 1 taken after heating for 30 minutes at a temperature of 120 ° C, respectively. The silver nanoparticles shown in Control 1 are present in a more granular form, while Sample No. 1 is more agglomerated into a three-dimensional structure, reducing the gap and thus reducing the voids therebetween.

As described above, the present invention provides a sinterable conductive composition comprising:

A metal component having an average particle diameter of greater than about 5 nm to about 100 mu m;

Subpayment; And

An emulsion comprising water and at least one polymer having an average particle diameter of about 5 nm to 1000 mu m.

In accordance with the present invention, a suitable sinterable conductive composition should have a VR of 1 x 10 < ^-4 >

In a more particular embodiment, the present invention provides a sinterable conductive composition comprising:

Metal components made or doped with silver, aluminum, gold, germanium or oxides or alloys thereof having an average particle diameter of greater than about 5 nm to about 100 mu m;

Phosphoric acid, phosphonic acid, formic acid, acetic acid, hydrogen halides and halide salts of metals of Groups I and II; And

An emulsion comprising at least about 95% water and at least one polymer having an average particle diameter of from about 5 nm to about 1000 [mu] m serving as a binder.

In another more particular embodiment, the present invention provides a sinterable conductive ink composition comprising:

A metal component having an average particle diameter of greater than about 5 nm to about 100 [mu] m; And

An emulsion comprising water and at least one polymer grafted with an organohalogen moiety having an average particle diameter of about 5 nm to 1000 mu m.

In another aspect, the invention provides a method of improving the electrical conductivity of a composition, comprising the steps of:

Providing an emulsion comprising water and at least one polymer having an average particle diameter of about 5 nm to 1000 mu m;

Providing a sub-settling to the emulsion;

Providing an emulsion with a metal component having an average particle diameter of greater than about 5 nm to about 100 mu m to form an ink composition; And

Exposing the composition to a temperature of from room temperature to about 200 < 0 > C for a time sufficient to sinter the ink composition.

In yet another aspect, the invention provides a substrate on which a composition of the present invention is disposed.

In yet another aspect, the present invention provides an emulsion comprising at least one polymer grafted with water and an organohalogen moiety.

In the conductive composition, in various embodiments, the metal component can be selected from metals made or doped with silver, aluminum, gold, germanium, or their oxides or alloys. The average particle diameter of the metal component is from about 20 nm to less than about 1 탆, for example, from about 200 to about 1000 nm.

If the metal component is silver, silver may be of any shape that is useful for commercial application. For example, silver spheres, rectangles, powders, and flakes are useful. Silver may be supplied as a dispersion in a suitable liquid vehicle or as a solid in a dried form.

Silver is commercially available from Ferro Corporation of Mayfield Heights, Ohio, Inframat Advanced Materials of Manchester, Conn., Or Metalor Technologies of North Attleboro, Mass. USA Corporation). ≪ / RTI > Mixtures of different sized silver flakes, such as a mixture of 11000-25 available from Ferro and 47MR-23S commercially available from Infra Mat may also be used.

Silver may be used in a range of from about 40 to about 99.5 weight percent of the composition, such as from about 60 to about 98 weight percent of the composition.

The polymer is selected from those made from monomers polymerized or copolymerized from styrene, butadiene, acrylic and methacrylic esters, chloroprene, vinyl chloride, vinyl acetate, acrylonitrile, acrylamide, ethylene, siloxane, epoxy, vinyl ether and many others . Particularly preferred polymers include polystyrene and polymethylmethacrylate.

The size of the polymer particles in the emulsion was measured with a static light scattering device called HORIBA LA-910, which provides an average particle size and particle size distribution.

The polymer molecular weights were measured by gel permeation chromatography, water 1525 pump, 2414 RI detector and 2487 UV detector, 717 autosampler, Empower 3 software. The linear and narrow molecular weight PMMA standards for calibration was used for determining the weight average molecular weight ( "M _w"), number average molecular weight ( "M _n") and the polydispersity _{( "M w / M n"} ).

In some embodiments, the polymer is grafted to an organohalogen moiety.

In some embodiments, the polymer is terminated with a diiodomethyl moiety.

The polymer should be present in the emulsion in an amount of 0.5 to 90% by weight, preferably about 10% by weight.

The ratio of the particle size of the metal component to the polymer should be from about 0.02 to about 50, such as from about 1.0 to about 0.1.

The emulsion may contain water in an amount up to about 95% by weight, such as up to about 50% by weight, preferably up to about 10% by weight.

The composition may comprise a sintering agent, which may be an acid or a salt, or may comprise a polymer grafted thereon, the organohalogen moiety acting as a sintering agent in part. However, any acid is not satisfactory. For example, sulfuric acid will not exhibit improved sintering or volume resistivity. However, hydrogen halides such as phosphoric acid, formic acid, acetic acid and hydrofluoric acid, hydrochloric acid, hydrobromic acid and iodine hydrobic acid will appear.

As sintering agents, halide salts of Group I and Group II metals such as sodium fluoride, sodium chloride, sodium bromide, sodium iodide, potassium fluoride, potassium chloride, potassium bromide, potassium iodide and the like may also be used.

The sieving is present in an amount from about 0.01% to about 10% by weight.

The sintering aid may be added in solid form, such as a halide salt, or may be added in a solution (not more than about 50 wt.%) Dissolved in water so that the ink of the present invention contains about 0.1 to 5 wt% Sintering aid concentration.

The conductive composition may comprise a surfactant. When surfactants are present, they may be selected from anionic surfactants containing anionic functional groups on their heads such as sulfates, sulfonates, phosphates and carboxylates. The major alkyl sulfates include ammonium lauryl sulfate, sodium lauryl sulfate [or sodium dodecyl sulfate (SDS)] and related alkyl-ether sulfates, sodium laureth sulfate [or sodium lauryl ether sulfate (SLES) < / RTI > and sodium maize sulphate. When a surfactant is present, the surfactant may be used in an amount of 10% by weight or less.

In addition, the conductive composition may comprise an organohalogen compound as a conductive promoter. Organohalogen compounds are liquid at room temperature. The organohalogen compound should have a boiling point of less than about 150 캜, such as less than about 120 캜, preferably less than about 100 캜, suitably more than about 70 캜. The organohalogen compound preferably has at least one iodine atom attached thereto. Preferably, only one iodine atom is attached to the organic iodide compound.

The organic moiety of the organohalogen compound may be alkyl or aryl. When it is alkyl, it must be lower alkyl wherein the alkyl moiety is 12 carbon atoms or less.

Representative examples of the organic halogen compound include 2-iodopropane, 1-iodopropane, 2-iodo-2-methylpropane, 2-iodobutane, 2-fluorobenzotrifluoride, 3- Fluoride, 4-fluorobenzotrifluoride, fluorobenzene, 2-fluoroethanol, 1-fluorododecane, 1-fluorohexane, 1-fluoroheptane and trifluoroacetic acid. Of course, mixtures of any two or more of these organohalogen compounds may also be used.

The organohalogen compound should be used in an amount of about 5% by weight or less. It has been demonstrated that preferably about 0.25% by weight is effective.

Table A provides a list of organohalogen compounds useful as conductivity promoters. An organohalogen compound having a boiling point of less than about 150 ° C minimizes the residue of the cured conductive ink.

Table A

Organohalogen compounds are useful for maintaining electrical conductivity while improving electrical conductivity of the composition and reducing loading of metal components.

It is often desirable to dilute the composition in a suitable solvent in order to be able to more easily dispense the conductive composition of the present invention. The dilution should be about 1 part of the composition to about 5 parts solvent. If the selected solvent is compatible with the organohalogen compound, many solvents are suitable for use in the compositions of the present invention.

The conductive compositions of the present invention are suitable for applications requiring high electrical conductivity on plastics such as PET and PC or other substrates.

Example

Example 1

The composition was prepared by dissolving polymethyl methacrylate emulsion (10% PMMA in water, 61 nm in water) in nano-particles (7K-35, known as DOWANOL with surfactant alcohol solvent, Ferroc Corporation, Ohio) Average particle size of PMMA, manufactured by Magsphere Corporation, Calif.). Sintering aid H ₃ PO ₄ (10 wt% in water) was added to Sample No. 1 and then mixed at 3000 rpm for 60 seconds. As a control, the performance against Sample No. 1 was compared using Control 1. Scanning electron microscopy ("SEM") images were obtained using Hitachi Field Emission SEM Model S-4500 and are shown in FIG.

Table 1

The compositions of Table 1 were each applied to glass slides and made as described herein to allow volume resistivity measurements.

The volume resistivity ("VR") of the prepared composition was measured by a standard strip method. Each specimen for the strip electrical conductivity test was prepared by first coating a thin layer on a glass slide that was masked with tape. The ink layer was dried at ambient temperature and then cured at the designed temperature over a set period of time. The resistivity was measured with a 4-probe ohm meter and the volume resistivity was calculated from the following equation: VR = (M) (T) (W _i ) / D, where M is the measured resistivity (in milliohms) T is the thickness of the strip in centimeters, cm, W _i is the width of the strip in cm, and D is the distance between the probes in cm.

Table 1A shows the values of the volume resistivity (ohm-cm) measured for the control 1 described in Table 1 and the composition of the present invention and the sample No. 1, respectively. The composition was prepared at a temperature of 120 캜 for a period of 30 minutes.

Table 1A

The PMMA emulsion and the sintering aid (aqueous H ₃ PO ₄ ) reduce the volume resistivity (Sample No. 1), the control group (only the nano silver paste is present), after heating for 30 minutes each at a temperature of 120 ° C, Lt; RTI ID = 0.0 > volume resistivity. ≪ / RTI > The addition of PMMA emulsion and H ₃ PO ₄ improved the electrical conductivity of silver ink by more than 10 times.

Taking both the resistivity measurements and the SEM results into account, it is deduced that the addition of the polymer emulsion and sintering aid to the compositions of the present invention helps the nanosilver to form a sintered and interconnected network and thus is much more conductive than the control composition .

Example 2

Four compositions were prepared by mixing nano-particles (7K-35, Mayfield Heights FerroCorporation, Ohio) with polystyrene emulsion (having various mean PSt particle sizes of 10% PSt, 62 nm, 200 nm and 600 nm in water, Manufactured by Magnesia Corporation, Pasadena, Calif.). Sintering aid H ₃ PO ₄ (10 wt% in water) was added to Sample Nos. 3, 4 and 5 and then mixed at 3000 rpm for 60 seconds. The so-formed composition was used to prepare test specimens.

Table 2

Table 2A shows the volume resistivity (in ohm-cm) measurements for the compositions of the present invention, Sample Nos. 2, 3 and 4, as described in Control 2 and Table 3, respectively. The composition was heated at a temperature of 120 DEG C for a period of 30 minutes.

Table 2A

Table 2A shows that the sintering aid (aqueous H ₃ PO ₄ ) reduces the volume resistivity of silver ink formulated with PSt emulsions (Sample Nos. 2, 3 and 4) after curing for a time of 30 minutes at a temperature of 120 ° C, The control (no sintering aid, H ₃ PO ₄ ) shows a higher volume resistivity. The addition of the sintering aid H ₃ PO ₄ improved the electrical conductivity of the silver ink composition with each PSt emulsion with different particle sizes (i.e., 62 nm, 200 nm, 600 nm). Thus, the compositions of the present invention have better electrical conductivity performance than the control composition. Within this defined sampling, the smaller the PSt particle size of the emulsion appears to be desirable in order to achieve excellent volume resistivity performance.

Example 3

The two compositions were prepared by mixing the nano-particles (7K-35, manufactured by Ferroc Corporation) with a polymethyl methacrylate emulsion (10% PMMA in water, having an average PMMA particle size of 61 nm). Two different sintering aids - H ₃ PO ₄ and KI (10 wt% in water, respectively) were selected. Sintering aid was added to Sample Nos. 5 and 6 and then mixed at 3000 rpm for 60 seconds. The so-formed composition was used to prepare test specimens.

Table 3

Table 3A shows the volume resistivity (in ohm-cm) measurements for the two inventive compositions, Sample Nos. 5 and 6, respectively, listed in Table 3 above. The composition was first cured at a temperature of 80 DEG C instead of a lower temperature-120 DEG C for a time period of 30 minutes.

TABLE 3A

Table 3A shows that the combination of each polymer emulsion and sintering aid reduces the volume resistivity of silver nanoparticle coatings (Sample Nos. 5 and 6) as compared to Control 1 (Table 1A).

Example 4

The synthesis of the iodine-grafted polymethylmethacrylate is illustrated as shown in the following scheme, where n is from 5 to 10,000.

130 g of DI water, of 2.0 g Brij 98 surfactant [polyoxyethylene oleyl _{ether, C 18 H 35 (OCH 2} CH 2) 20 OH] and 0.064 g (1 mmol), copper powder (<10 microns) of Was added to a 500-ml 4-necked round-bottomed flask equipped with a mechanical stirrer. 0.178 g (1 mmol) of Me ₆ TREN, 0.394 g (1 mmol) of iodoform and 20 g (200 mmol) of methyl methacrylate were added to a 50 milliliter Schlenk tube. Both mixtures were degassed by a freeze-pump-thaw cycle six times under a nitrogen atmosphere. The methyl methacrylate / Me ₆ TREN / CHI ₃ mixture was transferred via cannula to a round-bottomed flask under nitrogen. The polymerization reaction was continued for 5 hours at room temperature and stopped by the introduction of air.

Iodine-grafted PMMA was formed and dried at a temperature of 100 DEG C to yield a yield of 47%. By GPC analysis, the weight average molecular weight M _w was determined to be about 278,600, and the molecular weight distribution or polydispersity M _w / M _n was found to be about 3.3.

The emulsion particle size was measured with a Horiba LA-910 instrument and the median size was determined to be about 85 nm.

Example 5

Using iodine-grafted PMMA from Example 4, the nano-particles were prepared with a composition having (7K-35) to form an emulsion. The emulsion contained an iodine-grafted PMMA in an amount slightly greater than 55% by weight of the composition. No additional sintering aid was added; Rather, the iodine-grafted PMMA acted both as a binder and as a sintering aid. The composition was mixed at 3000 rpm for 60 seconds and then used to prepare test specimens.

Table 4

Table 4A shows the volume resistivity measurements (in ohm · cm) for the compositions of the present invention, Sample Nos. 5 and 7. The compositions were prepared at different temperatures-room temperature for 20 hours and at 80 占 for 30 minutes.

Table 4A

Table 4A shows that, regardless of the temperature and time used to cure the composition, the composition demonstrates reduced volume resistivity as compared to control 1 (Table 1A).

Example 6

The two compositions were prepared by mixing nano-particles (7K-35, manufactured by Ferroc Corporation) with polystyrene emulsion (49% PSt in water, Arkema Inc., Carry, NC). Sintering aid KI (3.5 wt% in water) was added to Sample No. 8, whereas D.I. Water was added to Control 3 instead, and they were mixed at 3000 rpm for 60 seconds. The so-formed composition was used to prepare test specimens.

Table 5

Table 5A shows the measurements of the volume resistivity (ohm · cm) for the two compositions, Control 3 and Sample 8, respectively, listed in Table 5 above. The composition was heated at a temperature of 100 DEG C for a period of 30 minutes.

Table 5A

Table 5A shows that the addition of the sintering aid KI reduces the volume resistivity of Sample No. 8 compared to Control 3. [

Example 7

The two compositions were prepared by mixing nano-particles (7K-35, manufactured by Ferroc Corporation) with a polystyrene emulsion (49% PSt in water, manufactured by Archemain Incorporated). Sintering aid 2-iodoethanol (5.0 wt% in water) and iodoacetamide (7.0 wt% in water) were added to Sample Nos. 9 and 10, respectively, and they were mixed at 3000 rpm for 60 seconds. The so-formed composition was used to prepare test specimens.

Table 6

Table 6A shows the measurements of the volume resistivity (in ohm-cm) for the two compositions, Samples Nos. 9 and 10, respectively, The composition was heated at a temperature of 80 DEG C for a period of 30 minutes.

Table 6A

Table 6A shows that the addition of an organic iodide compound as a conductivity promoter reduces the volume resistivity of Sample Nos. 9 and 10 as compared to Control 3.

Claims (31)

A metal component having an average particle diameter of greater than about 5 nm to about 100 [mu] m;
Subpayment; And
Water and an emulsion comprising at least one polymer having an average particle diameter of from about 5 nm to about 1000 &lt; RTI ID = 0.0 &gt; um. &Lt; / RTI &gt; The composition of claim 1, wherein the metal component has an average particle diameter of from about 200 nm to less than about 1 micrometer. The composition of claim 1, wherein the polymer has an average particle diameter of from about 20 to about 1000 nm. The composition of claim 1, wherein the polymer has at least one of a Tg greater than 70 DEG C or a molecular weight of about 200,000 Mw. The composition of claim 1, wherein the polymer is present in the emulsion in an amount of from 0.5 to 80% by weight. The composition according to claim 1, wherein the polymer is composed of monomers polymerized or copolymerized from styrene, butadiene, acrylic and methacrylic acid esters, chloroprene, vinyl chloride, vinyl acetate, acrylonitrile, acrylamide, ethylene, siloxane, epoxy and vinyl ethers Lt; / RTI &gt; is a member selected from the group consisting of The composition of claim 1, wherein the polymer is grafted to an organohalogen moiety. The composition of claim 1, wherein the polymer is terminated with a diiodomethyl moiety. The composition of claim 1, wherein the polymer is present in the emulsion in an amount of up to about 10% by weight. The composition of claim 1, further comprising a surfactant selected from the group consisting of anionic surfactants containing sulfate, sulfonate, phosphate and / or carboxylate groups. 11. The composition of claim 10, wherein the surfactant is present in an amount of up to 10% by weight. The composition of claim 1 wherein the sintering agent is an acid. The composition of claim 1 wherein the sieving is present in an amount from about 0.01% to about 10% by weight. The composition of claim 1, wherein the sintering agent is selected from phosphoric acid, phosphonic acid, formic acid, acetic acid, hydrogen halides and halide salts of metals of Groups I and II. The composition of claim 1, wherein the sintering agent is selected from hydrofluoric, hydrochloric, hydrobromic and iodinated hydrocarbons. The composition of claim 1, further comprising an organohalogen compound. The composition of claim 1, wherein the metal component is made or doped with silver, aluminum, gold, germanium, or an oxide or alloy thereof. The composition of claim 1, wherein the ratio of the metal component to the particle size of the polymer is from about 0.02 to about 50. The composition of claim 1, wherein the ratio of the metal component to the particle size of the polymer is from about 1.0 to about 0.1. The composition of claim 1, further comprising an organohalogen compound. 21. The composition of claim 20, wherein the organohalogen compound is liquid at room temperature. 21. The composition of claim 20 wherein the halogen of the organohalogen compound is iodine. 21. The composition of claim 20, wherein the organohalogen compound is a lower alkane halide. 21. The composition of claim 20, wherein the organohalogen compound is represented by a halogenated compound having up to 12 carbon atoms. 21. The composition of claim 20, wherein the organohalogen compound has a boiling point of less than about 150 &lt; 0 &gt; C. Metal components made or doped with silver, aluminum, gold, germanium or oxides or alloys thereof having an average particle diameter of greater than about 5 nm to about 100 mu m;
Phosphoric acid, formic acid, acetic acid, hydrogen halides and halide salts of metals of Groups I and II; And
Water and an emulsion comprising at least one polymer having an average particle diameter of from about 5 nm to about 1000 &lt; RTI ID = 0.0 &gt; um. &Lt; / RTI &gt; Providing an emulsion comprising water and at least one polymer having an average particle diameter of about 5 nm to 1000 mu m;
Providing a sub-settling to the emulsion;
Providing a metal component to the emulsion having an average particle diameter of greater than about 5 nm to about 100 mu m to form a conductive composition; And
Lt; RTI ID = 0.0 &gt; 200 C &lt; / RTI &gt; for a time sufficient to sinter the composition. A substrate on which the composition of claim 1 is disposed. A metal component having an average particle diameter of greater than about 5 nm to about 100 mu m; And
An emulsion comprising water and at least one polymer grafted with an organohalogen moiety having an average particle diameter of about 5 nm to 1000 mu m. 30. The composition of claim 29, wherein the polymer is terminated with a diiodomethyl moiety. An emulsion comprising at least one polymer grafted with water and an organic halogen moiety.

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